There is high comorbidity between the prevalence of post-traumatic stress disorder (PTSD) and alcohol use disorders (AUD) and this is a growing research area of interest. Current animal models have led to important insights into the neural circuits and molecular mechanisms involved in PTSD alone. However, despite the prevalence of AUD in patients with PTSD, there is a knowledge gap regarding the underlying neurobiology of comorbidity. This is due, in part, to the lack of animal models assessing the co-occurrence of PTSD and alcohol misuse. This is a critical topic, as validated animal models can lead to a better mechanistic understanding of the co-occurrence of these disorders, which may ultimately lead to more effective treatment strategies. In this application, we will combine a predator odor (PO) exposure model of PTSD with alcohol self- administration to model the emergence of maladaptive drinking patterns following development of PTSD from a traumatic experience. Studies in Aim 1 will focus on establishing and validating an animal model of PTSD and alcohol self-administration, along with cutoff behavioral criteria for use in the model. Studies in Aim 2 will probe adaptations in the Group II family of regulatory metabotropic glutamate receptors (mGluR2/3) as there is growing evidence for glutamatergic dysregulation in both PTSD and AUD. Studies in Aim 3 will focus on examining neural circuitry involving the nucleus reuniens, a midline thalamic nucleus, that has been emerging in the glutamatergic circuitry and symptom profile of PTSD, stress and depression. These studies represent an innovative strategy to advance understanding of mechanisms underlying susceptibility to increased alcohol drinking in PTSD.